fix(llm): add fetch-models endpoint, fix SQL Lab INSERT (client_id truncation, sync mode, target_column, timestamp normalization)

- Add POST /api/llm/providers/fetch-models route with LLMClient.fetch_models()
- Add target_column to TranslationJob model/schema/service/orchestrator
- Fix SQL Lab execute: truncate client_id to 11 chars (varchar(11))
- Switch SQL Lab to sync mode (runAsync: false) — no Celery workers
- Fix polling: unwrap nested result from Superset query API
- Fix ClickHouse timestamp: normalize float timestamps to YYYY-MM-DD

backend/src/services/dataset_review/clarification_engine.py

@@ -105,7 +105,6 @@ class ClarificationAnswerCommand:
 # @SIDE_EFFECT: Mutates clarification answers, session flags, and related clarification findings.
 class ClarificationEngine:
     # region ClarificationEngine_init [TYPE Function]
-    # @COMPLEXITY: 2
     # @PURPOSE: Bind repository dependency for clarification persistence operations.
     def __init__(self, repository: DatasetReviewSessionRepository) -> None:
         self.repository = repository
@@ -113,7 +112,6 @@ class ClarificationEngine:
     # endregion ClarificationEngine_init
 
     # region build_question_payload [TYPE Function]
-    # @COMPLEXITY: 4
     # @PURPOSE: Return the one active highest-priority clarification question payload.
     # @PRE: Session contains unresolved clarification state or a resumable clarification session.
     # @POST: Returns exactly one active/open question payload or None when no unresolved question remains.
@@ -173,7 +171,6 @@ class ClarificationEngine:
     # endregion build_question_payload
 
     # region record_answer [TYPE Function]
-    # @COMPLEXITY: 4
     # @PURPOSE: Persist one clarification answer before any pointer/readiness mutation.
     # @PRE: Target question belongs to the session's active clarification session and is still open.
     # @POST: Answer row is persisted before current-question pointer advances.
@@ -260,7 +257,6 @@ class ClarificationEngine:
     # endregion record_answer
 
     # region summarize_progress [TYPE Function]
-    # @COMPLEXITY: 1
     # @PURPOSE: Produce a compact progress summary for pause/resume and completion UX.
     def summarize_progress(self, clarification_session: ClarificationSession) -> str:
         resolved = count_resolved_questions(clarification_session)
@@ -270,7 +266,6 @@ class ClarificationEngine:
     # endregion summarize_progress
 
     # region _get_latest_clarification_session [TYPE Function]
-    # @COMPLEXITY: 2
     # @PURPOSE: Select the latest clarification session for the current dataset review aggregate.
     def _get_latest_clarification_session(self, session: DatasetReviewSession) -> Optional[ClarificationSession]:
         if not session.clarification_sessions:
@@ -281,7 +276,6 @@ class ClarificationEngine:
     # endregion _get_latest_clarification_session
 
     # region _find_question [TYPE Function]
-    # @COMPLEXITY: 1
     # @PURPOSE: Resolve a clarification question from the active clarification aggregate.
     def _find_question(self, clarification_session: ClarificationSession, question_id: str) -> Optional[ClarificationQuestion]:
         for q in clarification_session.questions: